Spectrally sensitized silver halide photographic emulsions

ABSTRACT

A silver halide photographic emulsion containing at least one sensitizing dye represented by the general formula:   HAS HIGH SPECTRAL SENSITIVITY IN THE VICINITY OF 460 - 490 M Mu . Moieties R1 - R4 are defined in the specification.

llnited States Patent Nakamura et al.

[4 1 Mar. 25, 1975 SPECTRALLY SENSITIZED SILVER HALIDE PHOTOGRAPHICEMULSIONS [75] Inventors: Yasuharu Nakamura; Yoshiyuki Nakazawa; TohruSueyoshi; Akira Sato; Tadashi ldeda, all of Kanagawa, Japan [73]Assignee: Fuji Photo Film Co., Ltd.,

Kanagawa, Japan [22] Filed: May 31, 1973 [21] App]. No.: 365,677

[30] Foreign Application Priority Data May 31, 1972 Japan 47-54497 [52]U.S. Cl. 96/120, 96/107 [51] Int. Cl G03c l/02 [58] Field of Search96/120, 107

[5 6] References Cited UNITED STATES PATENTS 2.111162 3/1938 Kendall96/120 141L507 11/1946 Collins ct al. 96/120 3.629374 l2/l97l Oliverlo/ill) Primary E.\'uminerJ. Travis Brown Attorney, Agent,0rF1'rmSughruc, Rothwcll, Mion, Zinn & Macpeak [5 7] ABSTRACT A silverhalide photographic emulsion containing at least one sensitizing dyerepresented by the general formula:

1 Cl N R; (I ca-ca =c 01 N has high spectral sensitivity in the vicinityof 460 490 mp. Moieties R, R4 are defined in the specification 7 Claims,1 Drawing Figure PATENTEDHARZ'J'IQB 3,873,323

SENSITIVITY+ WAVE LENGTH m u srEcTn A iLv s liiv sirlznii sitvan ii/tuna PHOTOGRAPHIC EMULSIONS BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to a silver halide photographicemulsion containing novel sensitizing dyes, and particularly to a silverhalide photographic emulsion having a high spectral sensitivity in thevicinity of 460 490 mu.

2. Description of the Prior Art In the manufacturing of silver halidephotographic emulsions it has been well known that when a sensitizingdye is added to the silver halide photographic emulsion the sensitivewave length region is expanded.

It has been well known that the spectrally sensitized wave length regionand the spectral sensitivity of silver halide photographic emulsionscontaining sensitizing dyes are influenced by the chemical structure ofthe sensitizing dyes and, especially, by the kinds of hetero rings andthe substituents on the sensitizing dyes.

Sensitizing dyes ofen display spectral sensitizations' which are notexpected at all due to a slight difference in chemical structure, andthe sensitization due to the J-aggregate (J-band) of sensitizing dyesdepends on the chemical structures of the sensitizing dyes.

The sensitization due to the J-aggregate of a sensitizing dye iseffective for the spectral sensitization in the region of a specifiedwave length, and it is very important to develop sensitizing dyes whichform the J aggregate in order to highly sensitize a specified wavelength region desired in the silver halide photographic sensitivematerial.

For example, the energy distribution of a light source used in thefacsimile field has a peak in the vicinity of 480 my. Therefore, it isdesirable that a photographic emulsion used in the facsimile art has amaximum sensitization in the vicinity of its peak, e.g., about 460 490mu.

However, there are little or no dyes which form the J-aggregate in thevicinity of 460 490 my and, if any do form the J-aggregate, thesensitivity thereof is too low.

SUMMARY OF THE INVENTION It has been found that new sensitizing dyeswhich are described in detail below are useful ones that form theJ-aggregate and strongly spectrally sensitize the wave lengths region inthe vicinity of 460 490 mu.

The object of this invention is to provide a silver halide photographicemulsion having high spectral sensitivity in the vicinity of 460 490 mJ., and it has been accomplished by adding to a silver halidephotographic emulsion novel sensitizing dyes of the following generalwherein R and R each represents identical or different alkyl groups asare conventionally used in cyanine dyes, i.e., both substituted andunsubstituted alkyl groups such as methyl, ethyl, n-propyl, n-butyl,carboxyalkyl (for example, carboxymethyl, B-carboxyethyl,'y-carboxypropyl, 8-carboxybutyl,etc.), alkoxyalkyl groups (for example,B-methoxyethyl), hydroxyalkyl groups (for example, B-hydroxyethyl etc.),acyloxyul kyl groups (for example, y-acetoxypropyl), sultoalkyl groups(for example, B-sulfoethyl, 'y-sulfopropyl. y-sulfobutyl, 8-sulfobutyl,etc.). aralkyl groups (for example, benzyl, phenethyl,p-carboxyphenethyl). vinylmethyl; and R and R may be identical ordifferent and each represents an acyl group, i.e., aromatic acyl group(e.g., benzoyl, etc.) or an aliphatic acyl group, preferably having upto 3 carbon atoms (e.g., acetyl, propionyl, etc.) or an alkoxycarbonylgroup (for example, methoxycarbonyl, ethoxycarbonyl, etc.).

In the above formulae, most preferred are those wherein any alkyl moietywhich is present contains up to 4 carbon atoms, except for the alkylmoiety of the alkoxy or alkoxy carbonyl group, which preferably containup to 3 carbon atoms.

As defined in general formula (I), the features of sensitizing dyes usedin this invention reside in the fact that they have a5,6-dichlorobenzimidazole nucleus as a hetero ring and an acyl oralkoxycarbonyl group as the terminal group. Those dyes having such achemical structure readily form the J-aggregate and are effective toincrease the spectral sensitivity in the vicinity of 460 490 mu.

BRIEF EXPLANATION OF DRAWING FIG. 1 shows spectral sensitivity curves,in which (a) shows the spectral sensitivity curve of a silver halidephotographic emulsion containing sensitizing dye (I) used in thisinvention and (b) shows the spectral sensitiviy curve of an otherwisedidentical emulsion where dye (I) is replaced with control sensitizingdye A.

DETAILED DESCRIPTION OF THE INVENTION Typical examples of the novelsensitizing dyes of general formula (I) which are used in this inventionare shown below, with the proviso that the sensitizing dyes used in thisinvention are not restricted to these examples.

Cl III COCII Dye 3 Cl N coca n =CH-CH=C c1 N I cooc a a Cl coca =caca=cc1 coca-t Dye 5 v (I3ZH5 Cl N coca U .=ca-ca=c c l \rlr COOC H Dye 6 c1/N coca =CHCH=C Cl 1T COOC2H5 A typical synthesis example of asensitizing dye used in this invention is as follows. Reference shouldalso be made to the text The Chemistry of Heterocyclic Compounds, TheCyanine Dyes and Related Compounds, Francis M. Hamer, lntersciencePublisher.

Ethyl-4-(5,6-dichloro-l,3-diethyl- Synthesis A of 2( 1H)-benzimidazolylidene )-2-acetyl-2-butenoate (Dye 1) 5 g of5,6-dichloro-1,3-diethyl-2-(B-N- acetylanilinovinylene) benzimidazoliumiodide and 2.5 g (100 percent excess) of acetoacetic acid ethyl esterwere dissolved in 6.0 ml of ethanol, 3 ml of triethylamine was added,the system heated for 1 hr. under reflux at atmospheric pressure, thencooled, and 300 ml of water added and the separated crystals subjectedto suction. The residue was treated with active carbon andrecrystallized two times from acetic acid ethyl ester to yield 3.0 g ofdye crystals (mp: l92- 194C, k 436 mu.

Other dyes can be synthesized readily by those skilled in the art with asynthetis method similar to the process as mentioned above merely byvarying the starting materials.

The sensitizing dyes used in this invention can spectrally sensitizesilver halide photographic emulsions and are especially effective toexpand the sensitivity region ol gclatino-silver halide photographicemulsions.

They can also sensitize silver halide photographic emulsions whichcontain gelatin derivatives such as acetylated gelatin, phthalatedgelatin, etc., hydrophilic colloids other than gelatin derivatives suchas cellulose 5 derivatives (e.g., carboxymethyl cellulose, celluloseether, partially hydrolyzed cellulose), polyvinyl alcohol, polyvinylpyrrolidone, copolymers of maleic anhydride and phthalic acid and othersynthetic or natural hydrophilic high molecular substances. Generally 10speaking, any photographic binder can be used with success in thepresent invention.

As the silver halide photographic emulsion used in this invention,various kinds of silver salts such as silver bromide, silveriodobromide, silver chlorobromide, silver chloroidobromide, etc., can beused and especially silver bromide and silver iodobromide emulsions areused effectively. So long as the silver halide is photosensitive, it canbe used with success in the present inen ion.

However, most preferred emulsions are those wherein the weight ratio ofsilver halide to binder is from about 4 about 1 to about 1 about 4.

The present invention is very effective when the silver halide used hasparticles which are normal or ultra linc grains (for example, those withan average particle diameter in number, measured by the projected areamethod, of less than about 0.1 u). The effect of this invention is moreremarkable for the ultra fine grains.

For the preparation of sensitized silver halide photographic emulsionsaccording to this invention, the sensitizing dye can be dissolved in asuitable solvent such as methanol, ethanol, methylcellosolve, etc., andadded as solution to a silver halide photographic emulsion in the mannercommonly used in this art. Suitable solvents are easily selected, theprimary considerations entering into the selection of the solvent beingthat the solvent is easy to handle, inexpensive, does not harmphotographic properties and is not injurious to the health. Organicsolvents miscible with water are generally used.

The amount of sensitizing dye contained in a silver halide photographicemulsion can be varied within, for example, a range of about 1 X 10 toabout 1 X 10 mol/mol of silver. Especially excellent results areobtained when the amount of sensitizing dye is about 5.8 X 10 mols/molof silver.

Additionally, any known sensitizing dye may be added to the silverhalide photographic emulsion according to this invention.

ln the preparation of a silver halide photographic emulsion according tothis invention, any commonly used chemical sensitizer, toner,film-hardener, antifogging agent, surface active agent, thickener,plasticizer, lubricant, development accelerator, color coupler,UV-absorbent, irradiation inhibitor, matting agent, etc., may be addedat proportions as are common in this art using any general additiontechnique.

The silver halide photographic emulsion according to this invention maybe coated by any technique commonly used in the art onto a suitablesubstrate such as, for example, glass, a film of cellulose derivatives(triacetyl cellulose, etc.), a film ofa synthetic resin (polyethyleneterephthalate, etc.), baryta paper, a resin-coated paper, syntheticpaper and the like. In short, any photographic substrate can be usedwith success in the present invention.

Several examples of preferred embodiments of the present invention aregiven below.

A given amount (8 ml per 100 g of emulsion) of a methanolic solution(1/l,000 mol of dye per liter of methanolic solution) of one of theabove mentioned sensitizing dyes used in this invention was individuallyadded to 100 g of a gelatino silver iodobromide emulsion ((I: Br ratio3:97 molar): ratio of silver halide:- binder 1:2 (weight); silver halideparticle size of 0.08 mu), which was prepared in a known method. 7 ml ofthe resulting silver halide photographic emulsion was coated on a glassplate of cabinet size and dried to prepare a sample.

The sample was exposed through a No. 2 filter (Fuji Photo Co., throughwhich light of a wave length longer than 450 mu passes) with an opticalwedge by means of a tungsten lamp having a color temperature of 2,666K(2,000 lux, 20 seconds) and then developed at 20C for 5 min with aliquid developer of the following formulation:

Metol Sodium sulfite Hydroquinone Anhydrous sodium carbonate Potassiumbromide 5 Water to make l liter.

In table 1, the spectral sensitivity, fog and maximum sensitization areshown for sensitizing dyes according to this invention as well ascontrol sensitizing dyes. FIG. 1 shows the spectral sensitivity curve ofdye (I) of this invention and of control dye A based upon the dataderived in this example.

TABLE 1 Ex. Dye Amount of Dye Sensitiza- Fog Maximum No. added tionsensiti- (n1ol/mol-Ag) degree zation l l 5.8 X I" 800 0.04 480 my. 2 2do. 400 0.04 475-480 mu 3 3 do. 750 0.04 480 mu 4 4 do. 350 0.04 475 mp.5 5 do. 600 0.04 480 my. 6 6 do. 650 0.04 480 mu A do. 100 0.04 458 m lCon- B do. I 0.04 465-470 my. trol C do. 110 0.04 465 mp.

D do. 120 0.04 460 mg The spectral sensitivity is shown under theheading Sensitization Degree" as a specific sensitivity where thesensitivity of sensitizing dye A used as a control is set as 100.

The chemical structures of the sensitizidng dyes which were used ascontrols are as follows:

O COOCH 5 C =CH-CH=C N & (300C 14 2 5 t Cl N CN D m =CHCH=C Cl lq COOC HAs is seen from the data in Table l, the emulsions containing thesensitizing dyes according to this inven tion have a sensitizationmaximum within the range of 460 490 mu and show little fog and highsensitivity as compared with the controls.

FIG. ll shows the spectral sensitivity curves of silver halidephotographic emulsions which contain novel sensitizing dye (I) used inthis invention and control sensitizing dye A, respectively.

As is seen from FIG. 1, sensitizing dye (I) used in this invention formsthe J-aggregate and has a high spectral sensitivity at 460 490 m,u.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:

l. A silver halide photographic emulsion characterized by containing atleast one sensitizing dye represented by the following general formula:

wherein R and R each represents an alkyl or substituted alkyl radicalselected from the group consisting of carboxyalkyl, alkoxyalkyl,hydroxyalkyl, acyloxyalkyl, sulfoalkyl and aralkyl, and R and R eachrepresents an acyl or alkoxycarbonyl radical.

2. A silver halide photographic emulsion as claimed in claim 1 wherein Rand R are unsubstituted alkyl.

3. A silver halide photographic emulsion as claimed in claim 1, whereinany alkyl moiety has up to 4 carbon atoms, with the exception of thealkyl moiety in the alkoxy group which has up to 3 carbon atoms.

4. A silver halide photographic emulsion as claimed in claim 3 whereinsaid acyl group is an aromatic acyl or aliphatic acyl group having up to3 carbon atoms.

5. A silver ahalide photographic emulsion as claimed in claim 4 whereinsaid aromatic acyl group is benzoyl.

6. A silver halide photographic emulsion as claimed in claim 4 whereinsaid silver halide has an average particle diameter, in number, of lessthan about 0.1 u.

7. A silver halide photographic emulsion as claimed in claim I whereinsaid sensitizing dye is present in an amount ol'l'rom about l X H) toabout I X l0 mollmololsilvcr. k

1. A SILVER HALIDE PHOTOGRAPHIC EMULSION CHARACTERIZED BY CONTAINING ATLEAST ONE SENSTIZING DYE REPRESENTED BY THE FOLLOWING GENERAL FORMULA:2. A silver halide photographic emulsion as claimed in claim 1 whereinR1 and R2 are unsubstituted alkyl.
 3. A silver halide photographicemulsion as claimed in claim 1, wherein any alkyl moiety has up to 4carbon atoms, with the exception of the alkyl moiety in the alkoxy groupwhich has up to 3 carbon atoms.
 4. A silver halide photographic emulsionas claimed in claim 3 wherein said acyl group is an aromatic acyl oraliphatic acyl group having up to 3 carbon atoms.
 5. A silver ahalidephotographic emulsion as claimed in claim 4 wherein said aromatic acylgroup is benzoyl.
 6. A silver halide photographic emulsion as claimed inclaim 4 wherein said silver halide has an average particle diameter, innumber, of less than about 0.1 Mu .
 7. A silver halide photographicemulsion as claimed in claim 1 wherein said sensitizing dye is presentin an amount of from about 1 X 10 3 to about 1 X 10 4 mol/mol of silver.